1. Field of the Invention
The present invention relates to an optical element and an optical element holder and, more particularly, to an optical element and an optical element holder with which position adjustment of the optical element can be preferably carried out.
2. Description of the Related Art
Conventionally, in an optical pickup device, a light-receiving element receives light that is emitted from a light source, irradiated to an optical disk and reflected thereby.
In such optical pickup device, conventionally, there have been a sensor lens provided at an incident-side position of the light-receiving element and a diffraction grating provided at an emission-side position of the light source.
The sensor lens has a function of giving astigmatism to the reflected light from the optical disk and of condensing the reflected light towards the light-receiving element. The diffraction grating has a function of converting and emitting the light emitted from the light source into three beams for tracking.
FIG. 10 and FIG. 11 illustrate an example of such sensor lens to be mounted on the optical pickup device. This sensor lens 1 is constituted of a lens main body 5 having two lens faces 2, 3, i.e. a first lens face 2 (cylindrical face) and a second lens face 3, and a cylindrical-shape holder 6 for holding the lens main body 5 from the outer side.
The lens main body 5 and the holder 6 are integrally molded by injection-molding of a resin material using a molding die.
Further, as shown in FIG. 10 and FIG. 11, on the outer-peripheral face of the holder 6, a position-adjusting concave part 7 with a square plane shape for adjusting the position of the sensor lens 1 is formed by caving into an optical axis 8 side.
The position-adjusting concave part 7 is capable of having an adjusting pin (not shown) inserted from the top end. In the state where the adjusting pin is inserted to the position-aligning concave part 7, the adjusting pin is moved in the optical axis 8 direction or rotated in the revolving direction with the optical axis 8 being the center, for example. With this, it is possible to adjust the position of the sensor lens 1 in the optical axis 8 direction, the revolving direction, etc.
For mounting such sensor lens 1 on the optical pickup device, the above-described position adjustment of the sensor lens 1 is performed on a frame of the optical pickup device and then the sensor lens 1 is fixed on the frame by means of an adhesive or the like, so that the reflected light from the optical disk can be appropriately guided to a light-receiving part of the light-receiving element.
The optical pickup device in which the position adjustment of the sensor lens 1 has been done can appropriately exhibit a desired function of the sensor lens 1. Therefore, it is possible to read out information, recorded on the optical disk and to write information on the optical disk appropriately.
Although not shown, like the sensor lens 1, the diffraction grating has a cylindrical-shape holder molded integrally on the outer side of the diffraction grating main body for holding the diffraction grating main body, and the same position-adjusting concave part as that of the sensor lens 1 is formed on the outer-peripheral face of the holder.
Like the sensor lens 1, such diffraction grating is also fixed to a frame by means of an adhesive and the like after performing the position adjustment on the frame.
[Patent Literature] Japanese Patent Unexamined Publication 60-234243
Conventionally, for molding the square position-adjusting concave part 7 as show in FIG. 10 and FIG. 11 by injection molding, it is necessary to prepare a slide molding die 11 (a section framed by slanting lines in FIG. 11) that is slidable in the radius direction used for molding the position-adjusting concave part 7 in addition to a lower die 9 that is a movable molding die for molding the first lens face 2 and an upper die 10 that is a fixed-side molding die for molding the second lens face 3 as shown by an alternate long and short dash line in FIG. 11.
That is, with the structure of the conventional position-adjusting concave part 7, it is essential to use the slide molding die 11 for surely taking out the molded article from the molding die in both cases where the position-adjusting concave part 7 is molded in the lower die 9 and in the upper die 10.
Therefore, conventionally, the cost of the molding dies 9, 10, and 11 is increased, resulting in an increase in the manufacturing cost of the sensor lens 1 molded in the molding dies 9, 10, and 11.
Further, there increases the generation rate of mold defects of the sensor lens 1 such as flash caused by the slide molding die 11, thereby deteriorating the yield.
Furthermore, in the case where an automation machine constituting a mass-production line of the sensor lens 1 is initially adopted, the cost of such automation machine comprising such molding dies 9, 10, 11 naturally becomes high since the cost of the molding dies 9, 10, 11 is high.
Moreover, there is also developed such a problem when modifying a current automation machine that it requires a tremendous amount of equipment cost for modifying the automation machine.
In addition, there are a large number of molding dies 9, 10, 11 so that it also requires a large amount of cost for the maintenance of the automation machine.
These problems exist not only in the sensor lens 1 but also in other optical elements such as the diffraction grating with the position-adjusting concave part, and in the case where the position-adjusting concave part is molded in a holder for holding an optical element, which is formed separately from the optical element.